1. Field of the Invention
This invention relates to treatment and prevention of Human Immunodeficiency Virus (HIV) by using a live genetically altered HIV virus vaccine.
2. Description of the Prior Art
To the best of this inventor""s knowledge, no prior art employing a similar invention for treatment or prevention exists.
Human Immunodeficiency Virus (HIV) is th e primary etiologic agent for the acquired immunodeficiency syndrome (AIDS). HIV exhibits high genetic variation, which results in a wide variety of biological phenotypes displayed by various strains of the virus and also by the same strain of the virus in a single patient at different times. Phenotypic heterogeneity is found in replication kinetics, susceptibility to serum neutralization, anti-viral drug resistance, induction of cytopathicity and host-cell range specificity. The two main sub-types HIV-1 and HIV-2 are members of a group of closely related human and non-human primate lentiviruses which are RNA retroviruses.
Infection by the HIV leads to progressive deterioration of cell mediated immune system making the victim susceptible to a variety of opportunistic infections such as pneumocystis carinii pneumonia (PCP) and tumors such as Kaposi""s sarcoma (KS). It is known that the mechanism of the destruction of the immune system is the cytopathic effect of HIV on CD4+ THELPER lymphocytes which are instrumental in proper functioning of cell mediated immunity.
AIDS and HIV infection initially involved homosexual men, intravenous drug users and hemophiliacs in the United States and Europe. However, heterosexual infection has become common and rampant in Africa (particularly in Rwanda, Burundi, Zaire and Kenya), Brazil, India, Myanmar and Thailand. According to the World Health Organization, in excess of 10,000,000 people world-wide are estimated to be infected with the HIV. The available data indicates that almost all of these infected individuals would die for lack of an effective treatment.
Humoral antibody response mediated by B Lymphocytes is usually strong in infected individuals with high antibody titres in those infected to the envelope proteins gp120, gp41 and gag proteins p24, p17 and p15. Unfortunately, this does not provide any protection from continued and relentless infection and progression of the disease mainly due to cell-to-cell transmission of infection and inhibition of cytotoxic T lymphocytes perhaps by inhibition of the IL-2 (interleukin 2) signalling. The US National Institutes of Health recently abandoned phase III and phase IV trials of vaccines derived from various viral proteins of HIV because of disappointing results in earlier phases. Similarly, cellular response against HIV is initially strong with an increase in cytotoxic (xe2x80x9ckillerxe2x80x9d) T lymphocytes (CTL). Unfortunately, this breaks down soon after infection due to genetic variations in the gag CTL epitopes which allows the virus to escape CTL recognition. (Phillips R E et al; Nature 345:453, 1991)
Various drugs have also been approved for treatment of HIV infection such as zidovudine which interfere with the virus""s nucleotide sequencing. While these were felt to be very promising in the earlier stages, development of resistance to them has caused a considerable amount of disappointment and frustration.
A variety of other approaches have been postulated. Professor Jonas Salk, in his commentary in Nature noted that as the disease progresses, titres of antibodies to gp41 and virus neutralizing antibody remain constant but the level of anti-p24 antibody which correlates with the presence of antibody dependent cell cytotoxicity (ADCC) and antibody to reverse transcriptase decline. He proposed treatment of symptomatic HIV infected patients with sera from asymptomatic HIV infected patients. He further hypothesized that HIV immunogens given to HIV infected patients would be protective. (Salk J; Prospects for the control of AIDS by immunizing seropositive individuals. Nature 327:473-476, 1987)
Live-attenuated viruses and dead virions have been hypothesized but no researcher has yet tried these either for prevention or treatment of HIV infection in humans in a meaningful manner.
SIV (Simian Immunodeficiency Virus) is a primate lentivirus with various strains that affect African green monkeys, macaque monkeys, sooty-mangabee monkeys, rhesus monkeys and chimpanzees. SIV infection in monkeys is widely used to study the physiology and pathology of the primate lentiviruses. A great deal of research has been done by attempting to infect monkeys with artificially created mutants of the SIV to determine their relative infectivity. Many of these studies focused on the role of the nef gene in the physiology of virus life cycle. The nef gene is present in all primate lentiviruses sequenced to-date. The gene consists of an open reading frame beginning within or immediately after the 3xe2x80x2 end of the env gene and overlaps the U3 portion of the 3xe2x80x2 long terminal repeat. The gene was previously named F, 3xe2x80x2-orf or B-orf. It is expressed in vivo as determined by antibodies to the nef gene product in infected individuals. Luria et al have shown that at least some nef gene products block the induction of IL-2 (interleukin 2) mRNA in lymphoid cells triggered by activating agents PMA, PHA and/or antibodies against CD3, TCR or CD2 (Luria S, Chambers I, Berg P; Proc Natl Acad Sci USA 88:5326, 1991). Kestler et al have found rapid reversion of of stop codon point mutations in nef to open forms in vivo, demonstrating selective pressure for open, presumably functional forms of nef. (Kestler H W et al; Cell, 65:651, 1991) It was further shown that nef is necessary for vigorous virus replication in rhesus monkeys, for maintaining normal virus loads and for induction of the disease. Animals inoculated with nef-deletion mutants have remained disease free for at least 3 years while wild-type virus infected animals all developed AIDS and died. It has also been demonstrated that nef deletion increases viral replication but it is postulated that the responses to nef deletion are different in vivo and in vitro. (Gibbs J S and Desrosiers R C in Human Retroviruses, Cullen B R, ed, Oxford University Press, NY, 1993)
It became the first object of this invention, therefore, to produce an HIV virus clone by utilizing recombinant technology in which a substantial portion of the nef gene is deleted while preserving the remaining open reading frames, particularly tat, pol, gag, env and vpr. It is a further object of this invention to inject patients infected with HIV with this nef deleted recombinant virus and provide a cure by means of one or more of
a) by allowing normal IL2 and IFNxcex3 production in THELPER cells thus activating B lymphocytes and cytotoxic (xe2x80x9ckillerxe2x80x9d) T lymphocytes (CTL) to recognize HIV antigen displaying cells,
b) by continually activating, stimulating and maintaining a cell mediated immune response to wild-type HIV via cytotoxic T Lymphocytes (CTL),
c) and by competing with the wild-type HIV for potential hosts and thus increasing the likelihood of exposure of the wild-type HIV to humoral antibodies to gp120, gp41 and gag proteins.
The second object of this invention is to provide prophylactic immunization in high risk individuals such as commercial sex workers by treatment with the nef deleted mutant virus which is a subject of this invention by providing a line of cytotoxic T lymphocytes with specificity to cells expressing any of the HIV proteins and which would create a semi-permanent memory stems of CTLs lasting a long time. Infection by wild-type HIV would, in these individuals be handled quickly, efficiently and effectively.
A recombinant clone of HIV-1ELI isolate with its nef open reading frame deleted was constructed from a plasmid vector by endonuclease cleaving at Nco I and Xho I sites and filling in the open ends with an oligonucleotide. The resultant plasmid DNA was screened and transfected by using DEAE dextran into HuT 78 cell line. HIV virus propagation was confirmed by monitoring proteins gp41, p24, p17 and p15, by monitoring reverse transcriptase activity and by electron micoscopic identification of virions. Virus particles were separated from supernatant medium and frozen in liquid nitrogen until use. For treatment of HIV infection, after baseline diagnostic procedures including confirmation of HIV infection and CD4-CD8 cell counts, a skin test for allegic reaction and an informed consent, approximately 200,000,000 virus particles will be injected intravenously. This will be followed by semimonthly monitoring of CD4 counts and a booster dose of another 200,000,000 virus particles intravenously. This will be followed by monthly monitoring of CD4 counts for one year. According to the invention, patients are expected to have a normal CD4 count in 6-9 months and will have restored immune systems in 1 year. For prevention of wild-type HIV infection in high risk populations, approximately 1,000,000 virus particles will be injected subcutaneously, the subjects observed for sufficient time to ensure absence of untoward effects such as an anaphylactic reaction. Immunity in this population will be ascertained by seroconversion and wild-type HIV infection can be diagnosed by utilizing enzyme linked immunosorbent assays for detection of antibodies to the nef gene product.
HuT 78 Cells, a human lymphoid cell line was obtained from the American Type Culture Collection (Rockville, Md.) and propagated in Dulbecco""s modified Eagle""s medium (Gibco, Grand Island, N.Y.) containing 10% heated (56xc2x0 F., 30 minutes) calf serum (Sigma Chemical Company, St. Louis, Mo.) and 10% interleukin 2xe2x80x94a T cell growth factor (Meloy laboratories, Springfield, Va.). Cells were grown on plastic tissue clulture dishes (Falcon) and transferred using trypsin with EDTA (Gibco, Grand Island, N.Y.). This cell line was inoculated with peripheral blood mononuclear cells (PBMCs) from an AIDS patient infected with the HIV-1ELI strain. The PBMCs were first prepared by banding over Ficoll-diatrizoate (density, 1.077 to 1.080 g/ml at 20xc2x0 C.)(Pharmacia LKB Biotechnology, Uppsala, Sweden). The PBMCs were washed with RPMI 1640 medium, stimulated for 5 days with 1 xcexcg/ml of phytohemagglutinin (Sigma Chemical Co., St. Louis, Mo.) and washed free of phytohemagglutinin prior to inoculation. The molecular cloning techniques were used as described by Maniatis T, Fritsch, EF et al (Molecular Cloning, a Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.). By using a non-cutter restriction endonuclease of HIV-1ELI (New England Biolabs, Beverly, Mass.) from total cell DNA of the infected cell line, integrated proviral DNA with flanking cellular sequences were cloned into the Xba I site of bacteriophage J1 (Promega Biotec, Madison, Wis.) giving rise to a recombinant phage clone xcexHXELI. A vector SP65gpt was constructed by ligating Bam HI-Pvu II fragment of plasmid pSV2gpt into the Bam HI-Pvu II sites of SP65 (Promega Biotec, Madison, Wis.). A 12.5 Kilobase (kb) Hpa I-Xba I fragment of the clone xcexHXELI was blunt-ended with Klenow fragment of DNA polymerase I and cloned into similarly blunt-ended Bam HI to Eco RI sites of vector SP65gpt. The resultant clone HXELIgpt had the HIV-1ELI and xanthine guanine phosphoribosyl transferase (gpt) sequences in identical transcriptional orientation. The provirus containing plasmid vector was digested with Nco I (Boehringer Mannheim Biochemicals, Mannheim, Germany) and Xho I (New England Biolabs, Beverly, Mass.) restriction endonucleases followed by a filling in the ends with an oligonucleotide constructed on a Biosearch Cyclone synthesizer, reverese transcriptase and dNTPs, followed by ligation of the blunt ends. Plasmids were screened by electrophoresis on 0.8% agarose gels (Sigma Chemicals, St. Louis, Mo.) for derivatives of HXELIgpt containing nef deletion. The exact coordinates of the deletion were confirmed by DNA sequencing with chain terminating inhibitors of DNA polymerase -2xe2x80x2,3xe2x80x2-dideoxy and arabinonucleoside analogues of the normal deoxynucleoside triphosphate (ddCTP was obtained from Collaborative Research, Inc., Waltham, Mass., araATP and araCTP were obtained from P-L Biochemicals, Inc., Milwaukee, Wis.) as described by Sanger, F, Nicklsen, S et al (Proc Natl Acad of Sci 74:5463-5467, 1977). Heteroduplex DNA was subjected to ethanol precipitation and and resuspended in sterile water. Serial dilutions of DNA were prepared to a final volume of 80 micL. To each sample of DNA was added 20 xcexcL DEAE dextran (molecular weight 5xc3x97105) obtained from Pharmacia in a concentration of 2 mg/ml after sterilizing by autoclaving and 100 xcexcL of two-fold concentrated serum-free Dulbecco""s modified Eagle""s medium (Gibco, Grand Island, N.Y.). The HuT 78 cells described above were transferred to fresh plates 24 hours prior to transfection to ascertain an exponential growth. These growing cells were removed from plates with 0.1% trypsin with EDTA (Gibco, Grand Island, N.Y.) in Tris-buffered isotonic saline at pH 7.2 (Sigma Chemicals, St. Louis, Mo.), mixed with fresh Dulbecco""s modified Eagle""s medium containing heated calf serum as described above to inactivate the trypsin and counted with a Coulter counter. 6xc3x97105 cells were added to 2 ml Dulbecco""s modified Eagle""s medium containing serum in 12 mmxc3x9775 mm clear plastic tubes (Falcon #2058). The tubes were centrifuged at 5000 rpm for 1 minute. The medium was withdrawn carefully using a pipette with an aspirator. A 100 xcexcL sample of the DNA dilution was added to each tube. The tubes were gently shaken and transferred to a 37xc2x0 C. CO2 incubator for 1 hr. The rack was gently shaken every 15 minutes. At the end of the incubation, 2 ml of fresh Dulbecco""s modified Eagle""s medium containing heated calf serum as described above was added to each tube, the tubes were shaken, centrifuged and the medium aspirated as described above. The cells were then resuspended in 2 ml of fresh Dulbecco""s modified Eagle""s medium containing heated calf serum as described above and incubated at 37xc2x0 C. in a 5% CO2 incubator. The cultures were monitored for appearance of HIV-1 gag and env products p17, p24 and gp41, reverse transcriptase activity and virions as seen by electron microscopy as is readily known to those knowledgeable in the art. Virus containing supernatant of the cultures was filtered through a millipore filter (filter size 0.45 xcexcm, Millipore Corp., Bedford, Mass.) and placed in sterile vials so as to contain about 200,000,000 virion particles per ml. The sterile vials were stored in liquid nitrogen.